Electrosurgery is a well known technology utilizing an applied electric current to cut, ablate or coagulate human or animal tissue. See U.S. Pat. No. 7,789,879 issued to Daniel V. Palanker et al., incorporated herein in its entirety by reference. Typical electrosurgical devices apply an electrical potential difference or a voltage difference between a cutting electrode and a portion of the patient's grounded body in a monopolar arrangement or between a cutting electrode and a return electrode in bipolar arrangement, to deliver electrical energy to the operative field where tissue is to be treated. The voltage is applied as a continuous train of high frequency pulses, typically in the RF (radio frequency) range.
The operating conditions of electrosurgical devices vary, see the above-referenced patent, in particular a configuration of the cutting electrode is described there whereby a conductive liquid medium surrounding the electrode is heated by the applied electric current to produce a vapor cavity around the cutting portion of the electrode and to ionize a gas inside a vapor cavity to produce a plasma. The presence of the plasma maintains electrical conductivity between the electrodes. The voltage applied between the electrodes is modulated in pulses having a modulation format selected to minimize the size of the vapor cavity, the rate of formation of vapor cavity and heat diffusion into the material as the material is cut with an edge of the cutting portion of the cutting electrode.
The operating principle thereby is based on formation of a thin layer of a plasma along the cutting portion of the cutting electrode. Typically some sort of conductive medium, such as saline solution or normally present bodily fluids, surround the cutting portion of the electrode such that the liquid medium is heated to produce a vapor cavity around the cutting portion. During heating an amount of the medium is vaporized to produce a gas inside a vapor cavity. Since typically the medium is saline solution or bodily fluids, the gas is composed primarily of water vapor. The layer of gas is ionized in the strong electric field or on the cutting electrode to make up the thin layer of plasma. Because the plasma is electrically conductive, it maintains electrical conductivity.
The energizing electrical energy modulation format in that patent includes pulses having a pulse duration in the range of 10 microseconds to 10 milliseconds. Preferably the pulses are composed of minipulses having a minipulse duration in the range of 0.1 to 10 microseconds and an interval ranging from 0.1 to 10 microseconds between the minipulses. Preferably the minipulse duration is selected in the range substantially between 0.2 and 5 microseconds and the interval between them is shorter than a lifetime of the vapor cavity. The peak power of the minipulses can be varied from minipulse to minipulse. Alternately, the minipulses are made up of micropulses where each micropulse has a duration of 0.1 to 1 microsecond.
Preferably the minipulses have alternating polarity, that is exhibit alternating positive and negative polarities. This modulation format limits the amount of charge transferred to the tissue and avoids various adverse tissue reactions such as muscle contractions and electroporation. Additional devices for preventing charge transfer to the biological tissue can be employed in combination with this modulation format or separately when the method is applied in performing electrosurgery. This pulsing regime is not limiting.
Typically the temperature of the cutting portion of the electrode is maintained between 40 and 1,000° C.
That patent also describes particular shapes of the electrode and especially its cutting portion in terms of shape and dimensionality. Such electrosurgical devices provide several surgical techniques, including cutting, bleeding control (coagulation) and tissue ablation. Typically different types of electrodes and energizing formats are used for various purposes since the amount of energy applied and the type of tissue being worked on differ depending on the surgical technique being used.
Further, it is known in the field for a single electrosurgery hand piece to have detachable electrodes, such as for instance a cutting electrode and a coagulation electrode. At any one time, only a single electrode is attached to the hand piece, see U.S. Pat. No. 5,984,918 issued to Garito et al. where multiple sized electrosurgical electrodes are connected to a handle using a collet member.
Therefore a known technical problem is that during a surgical procedure, the surgeon must switch between various types of electrosurgical equipment, at least by changing the electrode type. This is typically done by swapping between various electrodes either by changing the electrode portion applied to the body as in Garito et al., or by using entirely different sets of equipment for cutting and coagulation or ablation.
It has been found by the present inventors that this is undesirable and a better system would provide several types of surgical techniques using a single electrosurgical apparatus.